With the advent of stringent emission control standards for automobiles has come the need for an efficient, precisely operated fuel supply control system for internal combustion engines. One system under present consideration is the fuel injection system whereby fuel is injected into the intake manifold by an injector valve in accordance with commands from a control circuit. Precise control over the amount of fuel injected and the time it is injected is necessary in order to maintain emissions within certain limits and to operate the engine as efficiently as possible. In the prior art, this precise control was difficult and expensive to attain because prior art injector valves tend to be too slow in opening and exhibit non-linear control characteristics in certain ranges which make their control a more complicated problem. Thus, the need for a fuel injector valve with faster opening and closing times as well as more linear control characteristics is evident.
The fuel injection valves disclosed in U.S. Pat. Nos. 3,450,353; 3,592,392; 3,731,881 and 3,797,756 are typical prior art fuel injection valves. While each of the devices disclosed in these patents makes a definite improvement over prior art devices in opening and/or closing times and/or preciseness of operation, improvement is still needed in these areas. For example, typical prior art valves still exhibit non-linearities within certain operating ranges, thus making accurate control of the valve a difficult task.
In addition, U.S. Pat. No. 3,125,321 discloses a solenoid type valve in which a plunger member carries a valve member which mates with a valve seat to control flow from the inlet to an outlet. The valve disclosed in this patent is not specifically designed for use as a fuel injection valve.